Method of forming fibrous carbon articles



Feb. 1, 1966 R. L. BICKERDIKE ETAL METHOD OF FORMING FIBROUS CARBONARTICLES Filed June 22. 1960 ASSEMBLY OF STACK OF WOVEN FRABRIC DISCSIMPREGNATED WITH RESIN BETWEEN PRESSURE APPLYING MEMBERS 2 Sheets-Sheet1 ATMOS.

APPLICATION OF CONSTANT MECHANICAL PRESSURE WHILST SLOWLY HEATING THESTACK TO 400C IN NITROGEN AT GAS PRESSURE OF ONE REMOVAL OF STACK FROMPRESSURE APPLYING MEMBERS FURTHER HEATING TO IOOOC IN NITROGEN TOCOMPLETE CARBONISING HEATING FOR 90 HOURS AT 860C IN A BENZENE/NITROGENGAS STREAM TO DEPOSIT CARBON THROUGHOUT THE ARTICLE REMOVAL AND USE OFFURTHER OPTIONAL TREATMENT FOR 200 HOURS AT 860C IN A ARTICLEBENZENE/NITROGEN GAS STREAM REMOVAL AND USE OF ARTICLE INVENTORS ROBERTL. BICKERDIKE I GARYTH HUGHES BY Jzw QICCY ATTORNEY 8 Feb. 1, 1966 R.BICKERDIKE ETAL 3,233,014

METHOD OF FORMING FIBROUS CARBON ARTICLES Filed June 22. 1960 2Sheets-Sheet 2 ARTICLE CONSISTING OF DISC SHAPED LAYERS OF CARBONISEDWOVEN FRABRIC COMPRESSED IN THE DIRECTION OF THE ARROWS DURINGOARBONISING TO GENERATE CARBON BONDS BETWEEN THE DISCS WOVEN FRABRICDISCS FIG. 2

INVENTORS ROBERT L. BICKERDIKE GARYTH HUGHES ATTORNEYS United StatesPatent 3,233,014 METHOD OF FURMING FIBROUS CARBON ARTHCLES Robert LewisBicherdike, Farnharn, and Gaiyth Hughes,

Mytchett, Aldershot, England, assignors to United Kingdons Atomic EnergyAuthority, London, England Filed June 22, 196%), Ser. No. 37,832 Claimspriority, appiication Great Britain, July 2, 1959, 22,749/59 9 Claims.(Cl. 264-29) This invention relates to carbon and graphite materials.The term carbon will hereafter be used to described both.

Some of the important characteristics or carbon are that its strength isconsiderably greater in the basal plane of the crystals than in atransverse direction and its physical properties vary considerably withthe direction of the crystal. It is therefore necessary to consider theorientation of the structure of a carbon article with respect to itsproposed mode of use so as to try and make best use of these directionalproperties and the present invention is concerned with a new approach tothe problem of how to make best use of these properties.

Accordingly, the invention resides in the method of forming massivefibrous carbon material comprising carbon fibres which are the thermalconversion products of natural or synthetic organic fibres.

The material may include reactive material dispersed throughout as theprecipitate from a solution, or deposit from a vapour, or as particles,and the individual fibres may have on or around them a deposited skin orexternal layer or" carbon which may envelope the reactive material andthe fibres.

This skin may be derived from a liquid impregnant such as a syntheticresin which is converted to carbon or be laid down as carbon by thepyrolytic deposition of carbon from the vapour of a carbon compound. Theskin may be impermeable.

In some cases the material is impermeable as a whole or substantiallyso, the impermeability being brought about by the continuance or afurther application of the treatment employed for depositing the skin,this being continued. or repeated to fill the spaces between the fibresuntil a satisfactory degree of impermeability is achieved.

The material of the invention may be in the form of shaped articleswhich may have regions of greater density than the remainder, theseregions being impermeable if desired to constitute a barrier to thepassage of reaction products. For example a tubular article may comprisean annular impermeable region which prevents the passage of reactionproducts through the wall of the tube.

The process of making fibrous carbon material according to the inventionmay include assembling a structure of the organic or synthetic fibres,heating them in nonoxidising conditions to carbonising temperaturewhilst held in the desired form and, if desired, depositing externalcarbon layers on or around the individual carbon fibres of the mass by,for example, a pyrolytic deposition process in which the mass isheatedto a temperature above 500 C. in an atmosphere of, or in a streamof gas containing, a gaseous carbon compound. In such a process thetotal pressure may be about one atmosphere, but higher pressures may bebeneficial for higher deposition rates. The partial pressure of thecarbon compound should be adjusted to avoid the formation of soot in thefurnace under the combination of conditions obtaining. Alternatively themass of original organic fibres or the carbon fibres produced from themmay be impregnated by a pressure or evacuation technique with asynthetic carbon yielding resin, preferably. a furane derivative such asfurfuryl alcohol, which is subsequently polymerised and carbonised. Theprocess may include a final graphitising step at a temperature above2000 C. if desired.

Pyrolytic deposition may be continued until a high density and strengthare achieved, or the structure may be left with considerable residualporosity which has a beneficial effect on the physical properties of theproduct for some applications in that an unusually large deformationwill occur before complete fracture thereof when put under load.Pyrol'itic deposition may be continued for a sufiiciently long time torender the body substantially impermeable, at least at the outersurface. The pyrolysis may be performed on a free standing article orwhilst it is held in a mould or maintained under pressure.

The original fibres may be in the form of a random loose mass such ascotton Wool, or they may be spun or woven or subjected to some othertreatment to give them a required orientation or type of packing. If aloose fibre such as cotton wool is used, it is preferably compressedbefore carbonising, and it is desirable to restrict its expansion duringcarbonising by,.for example, holding it in a clamp or press to preventthe opening up of laminar flaws.

The process aforedescribed is depicted in FIGURE 1 which is adiagrammatic flow sheet. FIGURE 2 is an elevation, in partial section,of a laminar product made in accordance with the process depicted inFIGURE 1.

Part way through the pyrolytic deposition step the material or articlemay be graphitised by heating to a high temperature for example 2000 to2800 C. in a non-oxidising atmosphere. Further pyrolytic deposition maythereafter be performed and this produces a body with a duplex structureconsisting partly of soft graphitic material and partly of harderpyrolitic deposit. Alternatively the graphitising treatment may be donewhen deposition has been completed.

After pyrolytic deposition to the required extent, the material orarticle, if still porous, may be treated with a furane derivative suchas furfuryl alcohol as described above, the furfuryl alcohol beingpolymerised in the pores to a solid resin and this solid resin convertedto carbon or graphite in the pores by heating it to a temperature notless than 950 C.

The step of depositing reactive material through the basic fibrouscarbon material is advantageously performed before the step ofdepositing the carbon skin on or around the fibres so that the skinenvelopes the fibres or conjointly envelopes and joins togethercontiguous fibres and their attached reactive material.

The process of forming a shaped article of the basic material mayinclude the step of compressing the mass of organic fibres in a diebefore carbonising, at least during the period in which the mass israised to a temperature at which decomposition of the fibres occurs inthe first stage of their conversion to carbon.

Further, heating may be continued to the carbonising temperature whilstmaintaining constant, or varying, or removing the pressure and/ or theother conditions of the pyroyltic deposition process in a manner asdescribed. Advantageously pyrolysis is performed after reducing thetemperature slightly below the temperature employed during carbonising.In these conditions, with certain moulded shapes, if moulding pressureis maintained to above an optimum temperature in the carbonising cyclethe spontaneous shinkage of the fibre mass away from the walls of themould may cause buckling or distortion of the final product.

In the case in which the process of making the material or articleincludes impregnating a mass of the organic natural synthetic fibreswith a theromsetting adhesive resin, the process may comprise heatingthe mass to bring about cohesion of the fibres and set the adhesive andcompressing the mass in a die during at least part of the stage ofpolymerising or hardening the resin to make the article rigid,whereafter further pressure may be applied during carbonising. Theadhesive resin is desirably one which,

gives a high yield or carbon when decomposed by heat.

Furfuryl alcohol and phenol-formaldehyde resins are par,

substantially impermeable region such as an anunular impermeable region,the process may comprise arranging the original fibrous material to forma tube with a least a cylindrical intermediate zone having a higherfibre density than the remainder, carbonising the fibres and depositinglayers of carbon on the carbonisedfibres by a pyrolytic depositionprocess or by impregnation with a liquid synthetic resin as described.

The tubes may beconveniently formed by hydrostatically pressing a fibremass in a rubber bag. To obtain therequired high density of carbonisedmaterial in the middle of the wall, a loose layer of fibrous material isplaced round the outside of a thin walled rubber tube. Outside this isplaced a tube of closely woven material (either a natural or artificialWoven yarn). The woven tube is moistened with a furfuryl alcohol-acidmixture,

and outsideit a further layer of loose fibrous material is placed,followed by an outer rubber tube. The two rubber tubes are thenconnected to a hydrostatic pressure source and pressure applied.

After releasingthe pressure and extracting the pressed 'tube, it isfitted into a clamping device to prevent radial expansion of the outersurface or contraction of the inner, and carbonised. The carbonised tubeis finally given a pyrolytic deposition treatment.

Machining to final dimensions is accomplished part way through thepyrolytic treatment, before the material has become too hard. to turnsatisfactorily on a lathe.

Alternatively, rings of material woven to have a very dense fibrearrangement in a circular central zone may be arranged on a former aftermoistening with adhesive, such as furfuryl alcohol or a phenolformaldehyde resin, and subjected to slight axial compression whilstheated to polymerise the resin, and if.necessary, further pressure thenpacked in lamp black in a silica tube with graphite end plugs and slowlyheated to 1000 C. for 48 hours, and then cooled. The carbonised slab wasgiven a pyrolytic carbon deposition treatment by heating it in a silicatube furnace in a stream of nitrogen saturated with benzene as follows:

Benzene Period, hours Temperapartial Lure, C. pressure,

cm. Hg

The surface of the slab were then filed to remove the skin and pyrolysisrepeated for 21.5 hours at 845 to 850 C. at a benzene partial pressureof 8.2 cm. Hg and total v Each specimen was filed to remove the surfaceskin and further gas treated for 66 hours at 870 C.

during the'whole or part of a step sub-sequent heating to carbonise-thefibres. The high density zone gives a high density cylinder within thetube as a whole. Thereafter the fibrous carbon tube may be treated bypyrolysis and/ or given an impregnation and carbonising treatment in themanner described, by which treatment the dense inner cylinder rapidlybecomes a substantially impermeable cylindrical barrier. I

Ordinarycommercial cotton wool gives good results when used as thesurface layers of the tubes.

Several examples of the invention will now be de-. scribed:

Example I About 25 grams of compressed cotton wool was carbonised inlamp black in a silica vessel with a graphite sealing member by heating,slowly up to 1000 C. in a Nichrome furnace and then cooling over aperiod of three days, yielding about 7 grams of carbon fibres. Thecarbon fibre mass had an apparent density of 0.35 gr./cc. mass washeated in a streamof nitrogen saturated (at room temperature) withbenzene at 890 C. for 24 hours, after which the Weight was 20 grams andthe density slightly greater than 1 gram/ cc. On heating in a nitrogenandbenzene mixture as before for a further 19 hours at 850 C. thedensity increased to 1.4 g./cc.' Asample of the producthad a breakingstress in compression of 4.3 ton/sq. in.-

Example II Cotton Wool was compressed in a hydraulic press at a pressureof one ton per sq. in. into a slab approximately 3.75 X 1.5 X 1.5inches. This was held in a graphite clamp,

The

The density of the slab after carbonising and before pyrolysis was 0.25gm./cc. and the final'density of the specimens was 1.57 gm./cc. Whentested by bending, Youngs modulus was 2.07 10 p.s.i. and breaking stressin bending 11.6 tons/m comparedwith about 2 tons/ in. for conventionalcarbon material.

Example 111 It was desired to produce a solid cylinder of carboncontaining a dispersion of uranium in the central region completelyenclosed in a pyrolytic-carbon-filled outer case,

the whole forming one integral mass.

On to a disc of Woven cellulose material was laid a smaller diametersecond disc of finer spun and woven material containing a dispersionofuranium laid down from a solution of uranyl nitrate and precipitatedwith ammonia. Round the/edge of the smaller disc was laid a ring of thecoarser woven material of the same outer diameter as the lower disc.Another disc of the coarser material was laid on top of the samediameter as the first disc, and the laying up procedure was repeated. Inthisv way a column of material was built up, and by placing a number ofdiscs of the uranium-free material at the top and bottom of the column,the dispersed uranium was confined to the inner region of the column,leaving a uranium-free outer zone. All the discs were previouslymoistened slightly with acidified furfuryl alcohol and the column washeld under slight axial compression while the alcohol was polymerised toproduce a coherent column ready for carbonising. The column was heldunder slight axial pressure during carbonising and during the earlypartof a pyrolytic deposition process. Carbonising was carried outbyheating in a non-oxidising atmosphere to 1000 C., and after. adjustmentof the temperature to 860 C. a stream of nitrogen containing benzene(total pressure 1 atmos., benzene partial pressure 8 cm. Hg) was leadthrough the furnace to produce a deposit of pyrolytic carbon in thefibre mass. The outer uranium-free region, being of coarser fibre, wasmore easily penetrated by the diffusing gas than the inner region, withthe result that the uranium-containing zone was sealed by pyrolysisbefore the outer zone became impermeable. Pyrolysis was continued untilthe surface was completely sealed.

Using woven cloth a-uniform. controlled pore size is achieved, and noabnormally large pores occur, so that it is relatively easy to treat alarge, piece and make it impermeable.

Example IV About 20 grams of cotton linters were immersed at roomtemperature in a 10% solution of uranyl acetate in water. The surplusliquid was removed by light pressing and draining and the cotton wasthen put into 10% ammonia solution. After decanting and washing, thematerial was dried at 120 C. in an oven. Three 3 gram pellets were madeby taking 2.25 grams of untreated linters and 0.75 gram of the materialtreated as described and compressing in a dia. metal mould, the cottonbeing placed in the mould in such a way that the treated material wascompletely surrounded by the untreated.

The pellets were placed in a graphite clamp to prevent exfoliation,packed in lamp black in a silica tube with a graphite closure, andcarbonised by slow heating to 1000 C. over a period of 2 days. Aftercooling down and removing the lamp black, the specimens were given acarbon deposition treatment at 860 C. in a stream of nitrogen andbenzene vapour in a silica tube furnace, part way through which theywere removed from the furnace and ground fiat. The total gas pressurewas 1 atmosphere and the benzene partial pressure was 8 cms. Hg. Two ofthe specimens were given a pyrolytic carbon deposition treatment, onefor 7 /2 days and one for 11 days in the nitrogen-benzene atmosphere.The initial density (i.e. after canbonising) was about 0.5 gram/cc. andthe final density (after carbon deposition) about 1.46 grams/cc. Thespecimens were found to have good fission product (derived from the U235portion of the impregnant) retention characteristics after irradiationin an atomic pile.

Example V In an alternative to Example IV, 100 grams cotton linters waswetted with 280 cc. of a solution of uranyl nitrate in water (totaluranyl nitrate content 5 grams) by pouring the liquid on to the cottonand squeezing and releasing the latter alternately until it wasuniformly wetted. The damp cotton was then exposed to ammonia vapour bypassing over it a stream of nitrogen containing ammonia. After severalhours the ammonia content of the gas entering the vessel was reduced tozero, and the temperature was raised to 120 C. to dry the cotton, whichwas then compressed into pellet form both with and without extra undyedlinters, for processing as in Example IV.

Example VI A mass of cellulose fibre (cotton wool) was compressed underlight pressure in a die whilst the temperature was held at approximately450 C. At this temperature the fibres rapidly decomposed and an increasein apparent density of the mass occurred. When evolution of thevolatiles at 450 C. had ceased the temperature was raised to 1,000 C. tocomplete carbonising and the pressure maintained as carbonisaticnproceeded. The next step was to reduce the temperature to 900 C., stillmaintaining the pressure and pass through the die a stream ofnitrogen-benzene mixture (total pressure 1 atmos, benzene partialpressure 8 cms. Hg) whereby carbon was pyrolytically deposited on thecarbon fibres of the mass. The deposited carbon thus bonded the fibrestogether into a coherent porous mass. Pyrolysis was stopped when therewas a danger of bonding the mass to the die and the pres sure andtemperature reduced to normal. The fibrous article produced wasstructurally firm and strong enough to reisst delamination.

Example VII A pack of cloth discs was placed in a silica tube and slowlyheated to 400 C. in a stream of nitrogen at 1 atmosphere under aconstant mechanical pressure of 10 lbs/sq. inch. The temperature andpressure were maintained for 4- /2 hours until most of the volatiles hadbeen driven off. After cooling from 400 C., the compact which was fairlywell bonded, was removed. At this stage the density was 0.29 gram/cc. Itwas then heated to 1000 C. in a stream of nitrogen to complete carbonisation, and on cooling to room temperature the density was found to be0.31 gram/cc.

The specimen was then placed in a siilca tube and heated to 860 C., andnitrogen saturated (at room temt5 perature) with benzene was passed overthe specimen for hours. The total and partial gas pressures were asbefore. After cooling, the specimen was removed from tie furnace andmachined to give a regular shaped block of 3.7 cms. diameter x 2.1 cms.thick with a density of 1.0 gram/ cc.

After a further 200 hours treatment at 860 C. in the gas depositionfurnace the density of the block was 1.56 grams/cc.

Example VIII 20 layers of cotton Wool 2 /2 x 9" x A were placed one ontop of another and pressed under 50 tons. The compressed slab was heldin a graphite clamp which was then packed in lampblack and heated up to1000 C. over a period of 24 hours in order to carbonise the fibres. Theslab was removed from the lampblack and then treated for 65 hours atabout 860 C. in a stream of nitrogen saturated (at room temperature)with benzene. After cooling, the slab was cut into bars measuring 18.5crns. x 1.2 ems. x 1.2 ems, the density being 0.84 gram/ cc. The barswere then given a further 196 hours treatment at 860 C. in the gasdeposition furnace before grinding into test bars measuring square crosssection and 3 inches long. After a further 138 hours of similartreatment in the gas deposition furnace the density was 1.66 grams/cc.

Y oungs modulus determined by cantilever method gave an average value of341x10 psi. An average value of the bend strength measured by four pointloading was 6.7 tons/sq. inch. The compressive strength with the planeof compression perpendicular to the fibre length gave an average valueof 13.9 tons/sq. inch and when parallel to the fibre length the averagevalue was 19.5 tons/sq. inch.

After the final treatment in the gas deposition furnace some of the barswere graphitised by heating to 2800 C. for 6. hour in a graphite tubefurnace and mechanical tests then carried out on these bars in thegraphitised condition. The density of these bars was now 1.65 grams/ cc.An average value of the Youngs modulus was 196x10 p.s.i., and that ofthe bend strength 4.7 tons/ sq. inch. An average value of thecompressive strength when the plane of compression was perpendicular tothe fibre length was 6.1 tons/sq. inch, and when the plane ofcompression was parallel to the fibre length the average value was 8.1tons/ sq. inch.

Example IX A tube having high thermal conductivity across the wallthickness was made by stacking rings of woven cellulose yarn on aspindle to form a tube, each piece being lightly moistened withacidified furfuryl alcohol. The stack was then subjected to slight axialpressure and heated gently to polymerise the alcohol. Whenpolymerisation was complete the stack was carbonised by heating to 1000"C. in non-oxidising conditions and then treated by a pyrolyticdeposition process by heating it in a stream of nitrogen and benzene(total pressure 1 atmos, benzene partial pressure 8 cm. Hg) at atemperature of 890 C. After 48 hours, the stack was then heated to 2000C. in non-oxidising conditions to convert the carbon into graphite.

Example X In an alternative to Example EX, finely powderedphenol-formaldehyde resin was mixed with the original fibrous materialand compressed whilst heated to 180 C. to polymerise the resin. Blocksof the resulting resinirnpregnated fibrous solid were then carbonisedand treated by pyrolysis as in Example IX. 1

Example X! Small pieces of cotton wool were loosely packed into a silicatube and slowly heated to 1000 C. in an atmosphere of nitrogen in orderto carbonise the fibres. When 2 the furnace temperature was between 250and 500 C. light pressure was applied to graphite plungers at each endof the silica tube in order to compact the cotton wool and themechanical pressure was maintained until the carbonising was almostcomplete. After carbonising initia ly at 1000? C. the temperature of thefurnace was lowered to about 860 C., and nitrogen saturated (at roomtemperature) with benzene was passed through the compact for 17 hours.After cooling, the compact which was well bonded was removed from thetube. At this stage the material was. easily machinable, and a tube 1.25cms., inner diameter 2.70 ems, outside diameter 3.5 crns. long wasmachined from the compact, the density of the tube being 0.72 gram/ cc.The tube was then given a further treatment for 275 hours at 860 C. inthe gas deposition furnace, the final density being 1.58 grain/cc.

The permeability to air of the tube was then determined and found to be2.12 10* cn1. /sec. at room tem perature.

It is to be noted that in the cases in which the product of theinvention includes carbon deposited by pyrolysis that advantage is beingtaken of the orientated structure of carbon laid down in this way. Thusthe fact that the basal plane of the crystal of the deposited carbonmakes only a small angle with the underlying deposition surface has theeffect of restraining or impeding the movement of foreign atoms such asreaction products in a direction normal to the fibre axis. Thus theproducts of nuclear fission reactions would be largely retained withinthe deposited carbon skin.

A further advantage with respect to the inclusion inv the fibrousmaterial of reactive material is that a uniform and finely divideddispersion of reactive elements may be obtained throughout a carbonblock giving the advan tages as rcgardsreaction potential equivalent tousing a fine powder of reaction material but avoiding the physicaldisadvantages of handling and uniformly dispersing the powder in anymedium.

The preceding description is for the purpose of illustrating ourinvention, the scope of which is defined in the following claims.

We claim:

1. A process for making a block carbon article comprising the steps ofproviding a plurality of integral massive charges of organic fibers,each charge comprising a plurality of. discrete intermingled organicfibers, placing the charges in mutual contact between pressure applyingmembers,,providing and maintaining a non-oxidizing environment for thecharges, applying heat to carbonize the fibers and simultaneously urgingatleast one member to apply pressure to the charges, and maintaining thepressure during at least part of the carbonizing step, to produce ablock carbon article.

2. A process for making a block carbon article comprising the steps ofassembling a plurality of woven fiber discs in the form of a cylinder,providing and maintaining a non-oxidizing environment for the cylinder,heating the cylinder to carbonize the fibers and simultaneous? lycompressing the cylinder along its longitudinal axis, maintaining thepressure during at least part of the carbonizing procedure, and coolingthe carbonized article to provide a cylindrical block carbon article.

3. A process for making a block carbon article comprising the steps ofproviding a plurality of integral massive charges of organic fibers,each charge comprising a plurality of intermingled organic fibers;impregnating the charge of'organic fibers with a thermosetting adhesiveresin which resin will form a residue of substantially carbon whendecomposedby heat; placing the charges in mutual contact between.pressure applying members;

providing and maintaining a non-oxidizing environment for the charges;applying heat to the charges to crosslink the resin; applying additionalheat tothe charges to carbonize the fibers and the thermoset resin andsimultaneously urging at least one member to apply pressure to thecharges; and maintaining the pressure during at least part of thecarbonizing step to produce a block carbon article.

4. A process as claimed in claim .3 in which the resin is a furfuralalcohol.

5. A process as claimed in claim 3 in which the resin is aphenol-formaldehyde resin.

6. A process for making a block carbon article comprising the steps ofproviding a plurality of integral mas sive charges of organic fibers,each charge comprising a plurality of intermingled organic fibers;impregnating the charge of organic fibers with a thermosetting materialselected from the group consisting of furfural alcohol andphenol-formaldehyde resins; placing the charges in mutual contactbetween pressure applying members; providing and maintaining anon-oxidizing environment for the charges; applying heat to the chargesto polymerize said resin while simultaneously urging at least one memherto apply pressure vto the charges; applying additional eat to thecharges to carbonize the fibers and the resin and maintaining thepressure on the charge during at least part of the carbonizing step toproduce a block carbon article- 7. A process for making a block carbonarticle comprising the steps of assembling a plurality ofwoven fiberdisks in the form of a cylinder, impregnating thefiber discs with athermosetting adhesive resin which will form a residue of substantiallycarbon when decomposed by heat; providing and maintaining anon-oxidizing environment for the cylinder, heating the cylinder topolymerize the resin and simultaneously compressing the cylinder alongits longitudinal axis; applying additional heat to carbonize the fibersand said resin, maintaining the pressure during at least part of thecarbonizing procedure; and cooling the carbonized article to provide acylindrical block carbon article.

8. A process as claimed in claim 7 wherein the thermo setting resin isfurfural alcohol.

9. A process as claimed in claim 7 wherein the thermosetting resin isphenol-formaldehyde.

References Cited by the Examiner UNITED STATES PATENTS 275,612 4/1883Edison 20225 280,341 7/1883 Bernstein 202-25 X 349,572 9/1886 Dick 20226390,462 10/1888 Edison 3l3341 X 446,669 2/1891 Edison 313-343 X 470,9253/1892 Edison 264-29 494,150 3/1893 Loclyguine 117-4228 X 1,714,1655/1929 Gilbert 1854.7 X 2,817,605 12/1957 Sanz et al 117--228 2,972,5522/1961 Winter 117-46 2,997,744 8/1961 Stoddard 264-29 OTHER REFERENCESChem. Eng. 64, No. 10, 172 (1957).

Bickerdike et al.: Production of Impermeable Graphite;

Nuclear Power, February 1959, pp. 86-88.

Wide Use Predicted for New Graphite Fabric; Steel, May 11, 1959, p. 148.

RICHARD D. NEVIUS, Primaiy Examiner.

WILLIAM D. MARTIN, Examiner.

1. A PROCESS FOR MAKING A BLOCK CARBON ARTICLE COMPRISING THE STEPS OFPROVIDING A PLURALITY OF INTEGRAL MASSIVE CHARGES OF ORGANIC FIBERS,EACH CHARGE COMPRISING A PLURALITY OF DISCRETE INTERMINGLED ORGANICFIBERS, PLACING THE CHARGES IN MUTUAL CONTACT BETWEEN PRESSURE APPLYINGMEMBERS, PROVIDING AND MAINTAINING A NON-OXIDIZING ENVIRONMENT FOR THECHARGES, APPLYING HEAT TO CARBONIZE THE FIBERS AND SIMULTANEOUSLY URGINGAT LEAST ONE MEMBER TO APPLY PRESSURE TO THE CHARGES, AND MAINTAININGTHE PRESSURE DURING AT LEAST PART OF THE CARBONIZING STEP, TO PRODUCE ABLOCK CARBON ARTICLE.